Production of polyalkyl benzenes



United States Patent Qfiice 2,848,509 PRODUCTION OF POLYALKYL BENZENES William G. Toland, Jr., San Rafael, and L. G. Williams,

Richmond, Califl, assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application June 17, 1954 Serial No. 437,587 6 Claims. (Cl. 260668) This invention relates to a process for the production of polyalkyl benzene hydrocarbons. More particularly, it relates to an improved method for producing polymethyl benzene hydrocarbons in a manner adapted to yield a particular polymethyl benzene isomer of high purity.

Pursuant to the invention, polyalkyl benzenes having at least 3 alkyl groups substituted on the nucleus are prepared by a process which comprises reacting an aromatic hydrocarbon feed having a substantial content of dialkyl benzene hydrocarbons with formaldehyde to form a diarylmethane hydrocarbon product, subjecting the di-arylmethane to hydrogenolysis to produce alkyl benzene hydrocarbons and fractionally distilling the hydrogenolysis product to recover a polyalkyl benzene hydrocarbon having at least 3 alkyl groups substituted on the nucleus.

The process of the invention can be adapted to produce a variety of useful results. If any xylene isomer or a mixture of xylene isomers is condensed with formaldehyde to produce a di-xylyl methane and the dixylyl methane is then reacted with hydrogen under hydrogenolysis conditions, the di-xylyl methane molecule is split, producing one molecule of Xylene and one molecule of trimethyl benzene. The trimethyl benzene product is found to consist of about 90% or more by volume of pseudocumene, irrespective of which xylene isomer is used as the starting material. The process of the invention thus provides a means for obtaining pseudocumene in high purity without recourse to involved methods for separating the isomeric trirnethyl benzenes.

It is found, pursuant to the invention, that metaxylene condenses with formaldehyde to form a dixylyl methane much more rapidly than do ortho-xylene or para-xylene. It is thus possible to employ the process of the invention to manufacture pseudocumene and simultaneously produce a para-Xylene of high purity by charging a xylene feed which consists predominantly of metaxylene and para-xylene to the process and limiting the amount of formaldehyde charged to the process to 'a quantity stoichiometrically insufficient to condense all of the xylenes fed to the process to di-arylmethanes, but suflicient to condense the major proportion of the metaxylene fed to the process to di-arylmethane.

The process of the invention may also be employed to produce pseudocumene and a xylene product predominating in para-xylene by charging a mixture of xylenes and toluene to the process. The condensation product produced by reaction of this feed with formaldehyde will contain di-xylyl methane, xylyl tolyl methane and ditolyl methane. Hydrogenolysis of this reaction product will produce a mixture. of pseudocumene, xylene and toluene.

The process of the invention can also be employed to manufacture durene by condensation of xylenes with formaldehyde and hydrogenolysis of the product to pro duce high purity pseudocumene, which is then condensed with formaldehyde to form a di-pseudocumyl methane which, on hydrogenolysis, yields durene. By proceeding further, for example, by condensing durene with formaldehyde and hydrogenolysis, penta-methyl and hexamethyl benzenes can be produced.

It is possible to produce pseudocumene or higher polymethyl benzenes pursuant to the process by using either benzene or toluene as a starting material. If benzene is employed, the first hydrogenolysis product consists of benzene and toluene. When this product 'is' condensed with formaldehyde and subjected to hydrogenolysis, the resulting second hydrogenolysis product contains xylene, toluene and benzene. A further condensation and hydrogenolysis yields a product containing benzene, toluene, xylene and pseudocumene. A still further condensation of this product followed by hydrogenolysisyields a product containing benzene, toluene, xylene, pseudocumene and durene, etc. p

The reactions occurring in the process of the invention are illustrated by the following equations which show the production of pseudocumene and durene:

(1) CH3 CH5 OH; I

. acid 2 OH +HOHO OH catalyst CH CH5 CH3 on. on

CH3 if OH; CH3

CH5 0 a I Patented Aug. 1958 v i CH:

V I CH:

The process of the invention is illustrated by the following examples:

EXAMPLE 1 Table Paraxylene,

Ghnrge Stock 953% Xylene, mols Cs Formelln, mols H100 50 Wt. percent H2504, mols H1804. HiCoConversion (Mol'percent) after 0.5 hr. digestion after 2.0 hr. digestion-.--. after 2.5 hr. digestion after 3.0 hr. digestion Those runs made to isolate the trimethylbenzenes produced made use of the azeotroping technique of removing water of reaction from the condensation step as formed, permitting the use of less sulfuric acid than is necessary otherwise. The condensation products were washed free of acid and distilled to recover unconverted xylene, dixylylmethane, and polymer. The dixylylmethane was then passed over molybdena-alumina catalyst containing 8-12% molybdena with hydrogen and the products were distilled to obtain a. xylene fraction, :1 C aromatics cut, and unconverted dixylylmethane.

EXAMPLE 2 A 1I5-liter turbomixer, equipped with an inlet tube at the base, heating coil, thermowell, and reflux condenser with a water separator, was charged with 613.8 g. (700 cc.) (5.78 mols) of 97.0% ortho-xylene and 296.0 g. (190 cc.) (2.05 mols) of 67.5 weight percent sulfuric acid. The mixture was heated with stirring toreflux, giving a liquid-phase temperature of 263 F.-270 F. Aqueous formaldehyde solution (37% formalin) was then introduced through the inlet tube at the rate of 1 cc. per minut'e'until a totalof 82.2 g. (76 cc.) (1.01 mols) had been added. During this time, the reflux was controlled to remove water from the separator at essentially this same rate in order to maintaimaconstant concentration of acid in the reactor. A total of 71.0 g. (73 cc.) of water phase was collected and was found to contain 0.09 g. of formaldehyde.

The reaction products, weighing 912.3 g., were removed and cooled, permitting a separation of two liquid phases; an organic phase of 617.5 g. (680' cc.) and an aqueous phase of 293 g. (190 cc.), which was found to contain 66.8% sulfuric acid by weight. The acid layer was separated and the-organic phase washed with dilute caustic and water before distilling through a one-foot The 3 4 helices packed column to recover 389.9 g. (451 cc.) (3L67mols) of ortho-xylene, 189.1 g. (194 cc.) (0.845 mol) of diortho-xylylmethane boiling at 218 C.222 C. at 50 mm. of mercury,.and. 21.8 g. of higher polymer bottoms.

The conversion of formaldehyde was 99.7% and of ortho-xylene was 36.5%, to give an 80.2% yield of theory of dixylylmethanes from ortho-xylene and an 84.0% yield of theory from formaldehyde.

A total of 146 g. (150 cc.) of the diortho-xylylmethane was fed at a rate of 1 cc. per minute to the catalyst chamber with hydrogen fed at 6.0 cu. ft. per hour. The chamber consisted of a 30-inch vertical stainless steel pipe of %-inch I-. D. fitted with a /4-inch0. D. thermowell and heated by a-mercury bath under nitrogen pressure to 750 F. The catalyst, 49 g. (53 cc.) of pellets of molybdenum oxide (12% by Weight) on alumina formed a bed 13 inchesdeep. Liquid products, condensed in an ice trap followed by a Dry Ice cooled trap, consisted of 142.3 g. (156 cc.)'. Distillation through a three-foot helices-packed column yielded 32.8 g. (37.8 cc.) of ortho-xylene, boiling point 142 C.147 C.; an intermediatecut of 10 g., boiling point 147 C.-163 C.; a trimethylbenzene cut, boiling point 163 C.l69 C., of- 36.8 g.; and still bottoms-of recovered feed, 55.2 g.

Infrared" analysis of the trimethylbenzene fraction showed:

Volume percent (pseudocumene) is' 96.3%.

This shows'a 62.2% conversion of diortho-xylylmethane with a 70.8 mol percent yield of 1,2,4-trimethylbenzene.

EXAMPLE 3 The sameprocedure-and equipment was made as for ortho-xylene,'using' the. following materials in the indicatedquantities: 608 g. (700'cc.) (5.75 mols) of 96.3% meta-xylene, 301.2. g. cc.) (2.07 mols) of 67.5 weight percent sulfuric acid, and 82.8 g. (77 cc.) (1.02 mols) of 37% formalin. A totalof 73.0 g. (77 cc.) of water was removed during reaction by azeotroping and contained 0.006: g. formaldehyde; The reaction products'; 912 g., yielded 615.1 g. (685 cc.) of. organic layer and 296'.0 g. (190 cc.) of aqueous acid phase of 65.8% sulfuric acidby weight. After distillation, there was obtained 368.0 g; (427 cc.) (3.47 mols) of meta-xylene, 188.9'g. cc.) (05844 mol) of dimeta-xylylmethane boiling at" 211' CI21 5"' C. at 50 mmof mercury, and 18.6 "g; of higher polymer bottoms.

The conversion of formaldehyde was 99.9% and of meta-xylene was 39.7%, to give a yield of dimeta-xylylmethane of 74.2% of theory from meta-xylene and of 83.0% of theory from formaldehyde.

Following the same procedure used in Example 2, 144 g. (150. cc.) of dimeta-xylylmethane was fed with hy' drogen over the catalyst bed. Liquid products, 142.7 g. (158 cc.) on fractional: distillation, gave 42.1 g. of memxylene, boiling point 138, C.-145 C.; 6.0 g. of an intermediate fraction, boilingpoint 145 C.-163 C.; 43.7 g. of a trimethylbenzene' fraction; and 45.1 g. of unconvertedfeed.

Infrared analysis of the trimethylb'enzene fraction showed:

Of the C aromatics, the 1,2,4trimethylbenzene (pseudocumene) is 95.2%.

This shows a 68.8% conversion of dimeta-xylylmethane with a 76.6 mol percent yield of pseudocumene in a single pass.

EXAMPLE 4 Again using the same equipment and procedure as for ortho-xylene, in Example 2, the following materials in the indicated quantities were employed: 602.8 g. (700 cc.) (5.68 mols) of 95.2% para-xylene, 302.5 g. (192 cc.) (2.06 mols) of 68 weight percent sulfuric acid, and 82.7 g. (77 cc.) (1.02 mols) of 37% formalin. A total of 73.8 g. (74.8 cc.) of water was removed by azeotroping and was found to contain 0.03 g. of formaldehyde.

The reaction products, 897.3 g., yielded 538.7 g. (608 cc.) of organic layer and 349.1 g. of an acid emulsion. Caustic treating resulted in a 162.5 g. loss in weight of the organic layer, from which some paraxylene was later recovered by stripping. An additional increment was recovered similarly from the acid emulsion. Distillation of the organic phaseyielded 237.9 g. of para-xylene, 121.7 g. of dipara-xylylmethane, a white crystalline solid 'at room temperature which boiled at 202 C.-207 C. at 50 mm. of mercury, and 1-5.4.g. higher polymer bottoms.

.The conversion of formaldehyde was 99.9% and of para-xylene was 41.7%, to give'a yield of dipara-xylylmethane of 70.8% of theory from para-xylene and of 81.6% of theory from formaldehydeincluding the products recoverable from the-emulsions.-

Because dipara-Xylylmethane is a solid at room temperature, it was dissolved in benzene to give a 50 weight percent solution, which was introduced at 4 cc. per minute with 6 cu. ft. per hour of hydrogen through the same equipment and catalyst bed as before, at 750 F., until a total of 1003 g. (1093 cc.) of solution, containing 501.5 g. of dipara-xylylmethane, had been fed. -A total of 992.5 g. of liquid products was recovered, which on distillation gave 502.5 g. of benzene; 9.8 g. of intermediate boiling to 137 C.; a para-xylene fraction of 45.4 g., boiling point 137 C.-140 C.; and intermediate fraction, boiling from 141 C. to 166 C. of 23.6 g.; a trimethylbenzene fraction of 43.5 g., boiling point 166 C.-169.5 C.; and recovered dipara-xylylmethane, 362.5.g.

Infrared analysis of the trimethylbenzene fraction showed:

Volume percent Xylenes 1.5 1,2,4-trimethylbenzene 97.5 1,2,3-trimethylbenzene 0.5 l,3,5-trimethylben7ene 0.3

Total 99.8

EXAMPLE Using the same equipment and procedure as in Example 2, the following materials in the indicated quantities were charged: 395.9 g. (460 cc.) (3.99 mols) of mixed xylene- .toluene blend of the followingi composfition (infrared analysis) Volume percent Ethylbe 1.2 Ortho-xylene 16.8 Meta-xylene---" 17.7 Para-xylene 17.2 Toluene 45.6

Total 98.5

plus 91.9 g. (60 cc.) (0.645 mol) of 68.7 weight percent sulfuric acid, and 81.5 g. (76 cc.) (1.02 mols) of 37% formaldehyde solution (formalin). A total of 76.4 g. (78 cc.) of water was removed by azeotroping and was found to contain 0.92 g. of-formaldehyde. The reaction products, 505.0 g., yielded 392.2 g. (430 cc.)

of organic layer and 110.1 g. (79 cc.) of an acid emul- Ethylberwene 0 Ortho-xylene 18.5 Meta-xylene 5.7 Para-xylene 22.4 Toluene 52.8

Total 99.4

The conversion of the formaldehyde was 97.3% and of the aromatics was 44.8 mol percent to give a yield of di-arylmethanes of 85.3% of theory from the aromatics and 77.0% of theory from formaldehyde. The'conversions ofthe individual organic compounds were for the ethyl'benzene, 60% for ortho-xylene, 83% for meta-xylene, 30% for para-xylene and 37% for toluene.

Following the same procedure used in Example 2, 141.7 g. cc.) (0.665 mol) of the di-arylmethanes was fed with hydrogen over the catalyst bed. Liquid products, 138.6 g. (151 cc.)'on fractional distillation gave 47.7 g. (56 cc.) of a toluene-xylene fraction boiling. at 111 C.- C.; a trimethylbenzene fraction, boiling range 160 C.- C., of 16.2 g. (18.5'cc.); and a still bottoms of recovered di-arylmethanes, 66.0 g.

Infrared analysis of the toluene-xylene fraction showed:

Volume percent Infrared analysis of the trimethylbenzene fraction showed:

Volume percent 5 0 Ortho-xylene 1,2,4-trimethylbenzene 85.0 1,3,5-trimethylbenzene 0.5 1,2,3-trimethylbenzene 8.0

Total 98.5

This run showed a 53.5% conversion of di-arylmethanes per single converter pass operation.

Adjusting all analysis data to 100 volume percent totals, and then normalizing for organic handling losses in the condensation and hydrogenolysis steps, the net absolute conversions and yields for the two-step process (based upon a 100% hydrogenoly'sis conversion of the. di-arylmethane feed stock) may be tabulated as follows:

( (B) MB) Net- Condensation Hydrogenolysls Con-, Net Conversions Yields ver- Yield slon' g mols g mols mols mols Ethylbenzene 4.7 0. 044 1.9 rth0xylene.. 27. 4 0. 258 21. 8 Meta-xylene- 59. 0 0. 557 43. 4 Para-xylene.. 20. 4 0. 192 36. 8 Toluene 67.9 0. 738 11.3 1, 2, 4-trlmethylbenzene 39. 0 1,2, 3-trlmethylbenzene.-- 3.4 1, 3, -trim'ethylhenzene. 0. 2

Totals 119.4 1. 789 163. s

('CH1) from ECHO 13. 9 0.99 Di-arylmethaneyleld- 1.524/N1 Polymer yield 31. 0 0; 265/N:

EXAMPLE 6 Volume percent 4 Ortho-xylene 8 Using the same equipment and procedure as in EX- ample, 2, the followingmaterials in the indicated quantiigi'f t t fi ig 1 ties were charged: 434.8 g. (501 cc.) (3.84 mols) aro- E 61 matic feed stock of the following composition as analyzed mc enzene 5 by infrared methods: 1,2,4,5 -tetramethylbenzcne 23 1,2,3,5-tetramethylbenzene 2 Volume percent Meta-xylene 1 Total 100 Ortho-xylene 48 I 1 3,54 -imethy1benzene 0.5 Normalizing for organic handling losses in the conl z 4 trimethylbenzene 1 48 de'nsatio'n and hydrogenolysis steps, and comparing over- 1 2 3 t -imefl1y1benzene 2 all absolute conversions and yields for the two-step process, it may be seen that this particular reaction was a Total 995 breeder reaction. The amount of pseudocumene con- 40 vetted todurenewas replaced bythe ortho-xylene con- 1 Pseudocurnene.

Volume percent ortho xylene 62.0

1,2,4-trimethylbenzene .37.0 I

1,2,3-trimethylbenzene 1.0

Total 100.0

plus 198.1 g. (200cc) of co-condensation productshoiling at 220 C.240 C. at mm. of mercury, and 26.2

g. of higher polymer bottoms.

The conversion of formaldehyde was 99.7% of orthoxylene was 38.6% and of pseudocumene was 63.2% to give a di-arylmethane yield of 82.8% based on aromatics converted.

Following the same procedure used in Example 2, 180.5 g. (190 cc.) of the di-arylmethanes was fed with hyodrogen over the catalyst bed. Liquid products, 176.8 g. (199 cc.) on fractional distillation gave 140.6 g. (160 cc.) of hydrogenolysis products, boiling range 160 C.- 214 C. at 760 mm. of mercury, and 33.5 g. (34 cc.) of unconverted di-arylmethancs, boiling range 218'-242 C. at 50 mm. of mercury.

Infrared analysis of the hydrogenolysis'product'fraction showed:

verted to pseudocumene. The net consumption of orthoxylenewas 0.60mo1 and the net production of durene was 0.36 mol.

EXAMPLE 7 Using the same equipment and procedume as in Example 2, the following. chemicals in the indicated quantitieswere charged: 272.0 g. (312 cc.) (2.57 mols) of toluene-pseudocumene blend of the following composition:

Volume percent Toluene 44.2 Ortho-xylene 1.6 1,3;5-trimethylbenzene 0.1 1,2,4-trimethylbenzene 49.6 1,2,3-trimethylbenzene 4.5

Total 100.0

plus 1.140 g. (740 .cc.) (7.48 mols) of 64.2 weight percent sulfuric acid, and 49 g. (45 cc.) (0.604 mol) of formalin (37% formaldehyde). A total of 46.7 g. (47 cc.) of water was removed by azeotroping and was found to contain 0.049g. of'formaldehyde. The reaction products yielded 268.7 g. of organic layer and 1075.6 g. of 4 The second distillation fraction, boiling range 116 C.- 170 C. at 760 mm. of mercury, of 44.3 g. (54 cc.) was found by analysis to have the following composition:

Volume percent Toluene 12 0 Ortho-xyl n 4 1,3,5-t1imethylben7ene Q2 1,2,4-trimethylbenzene 79.8 1,2,3-trimethylben1ene 4 Total 100.0

The conversion of formaldehyde was 99.8% and of the aromatic feed stock was 52.7 mol percent to give an actual yield of di-arylmethanes of 78.6 weight percent based on the weight of aromatic feed stock and formaldehyde converted. The yield of di-arylmethanes can be increased by contacting the caustic treat emulsion layer with fresh or recycle organic feed en route to the condensation step. Normalizing for this additional possible recovery, the total aromatic conversion is 47.1 mol percent and the weight percent yield of di-arylmethanes is 96%. On this normalized basis, the individual aromatic conversions are 25 mol percent toluene, 19 mol percent ortho-xylene, 71 mol percent 1,2,4-trimethy1benzene and 84 mol percent 1,2,3-trimethylbenzene.

Following the same procedure used in Example 2, 101.8 g. (107.5 cc. liquid volume at 80 C.) of the diarylmethanes was fed with hydrogen over the catalyst bed. Liquid'products, 98.7 g., on fractional distillation gave 9.8 g. (12 cc.) of a toluene-xylene fraction boiling at 121 C.-l45 C.; a trimethylbenzene fraction, boiling range 146 C.184 C., of 41.4 g. (48.0 cc.); a tetramethylbenzene fraction, boiling range 194 C.-215 C. at 760 mm. of mercury, of 26.1 g.; and a still bottoms of recovered di-arylmethanes, 17.7 g. (liquid at 20 C.).

The composition of the toluene-xylene fraction was:

Volume percent Ethylbenzene 1.0 Toluene 28.5 Ortho-oxylene 15.3 Meta-xylene 3.5 Para-xyl n 50.7 1,2,4-trimethy1ben7ene 1.0

Total 100.0

The composition of the trimethylbenzene fraction was:

Volume percent Ortho-xylene--- 3 The composition of the tetramethylbenzene fraction was:

Volume percent 1,2,4-trimethylbenzene 8 1,2,4,5-tetramethylbenzene 85 1,2,3,5-tetramethylben 7 To al 100 The di-arylmethane conversion for this single 'pass'hydrogenolysis was 82.5 weight percent. Normalizing for organic handling losses in the two-step process, and balancing absolute conversions against calculated absolute yields from an extrapolated di-arylmet'hane conversion in the hydrogenolysis step, an overall two-step process yield of 119 mol percent durene from pseudocumene and only 56 mol percent xylenes from toluene was calculated. The recovered feed stock from the single pass hydrogenolysis was a homogeneous liquid phase at 20 C., and contained very little or none of the dipseudocumal methane, as evidenced by the lack of crystallinity, even upon seeding the recovered feed with the original condensation product crystals. For this reason and the fact that recycle hydrogenolysis of this recovered feed yielded additional toluene, xylenes, pseudocumene and durene, it is clear that the recycle feed stock was composed mainly of the ditolylmethanes and tolylpseudocumal methanes.

EXAMPLE 8 Using the same equipment and procedure as in Example 2, the following materials in the indicated quantities were charged: 600 g. (700 cc.) (5.66 mols) of mixed xylenes of the following composition:

Volume percent Para-xylene 65.8 Meta-xylene 4.2 Who-Xylene 24.4

Total 94.4

Volume percent Para-xylene--- 74.8 Meta-xylen 0.9 Ortho-xylene 20.2 Ethylbenzene--- 0.5

plus 164.5 g. (168 cc.) (0.768 mol) of the di-xylylmethanes boiling at 204 C.-216 C. at 50 mm. of mercury, and 20.5 g. of higher polymer bottoms.

The conversion of formaldehyde was 99.7% and of the xylenes was 33.5% to give a yield of di-xylylmethanes of 81.5% of theory from the xylenes and 86.8% of theory from formaldehyde. The conversions of the individual xylene isomers were 25% for the para-xylene, 86% for the meta-xylene and 45% for the ortho-xylefi. The condensation resulted in a net upgrading of the paraxylene/meta-Xylene ratio from 94/ 6 to 99/ l, which allows the remaining ortho-xylene to be removed by distillation to yield a high purity (95% para-xylene fraction.

Following the same procedure used in Example 2, 143.6 g. cc.) (0.64 mol) of the di-xylylmethanes were fed with hydrogen over the catalyst bed. Liquid products, 140.8 g. (154 cc.) on fractional distillation gave 44.3 g. (51.3 cc.) of xylene fraction, boiling range 137 C.- C.; a trimet-hylbenzene fraction, boiling range 163 C.-l70 C., of 43.6 g. (50.4 cc.); and still bottoms of recovered feed, 45.9 g.,

1 1 Infrared analysis of the'xylenefraction showed:

Volume percent 1.0

Ethylbenz'ene Ortho-xylene 23.1 Meta-xylene 20.1 Para-xylene 5 6.1 1,2,4-1Iimethylbenzene 2.7

Total 103.0

Infrared analysis of the 'trimethylbenzene fraction showed:

. Volume percent This shows a 68.3% conversion of the di-xylylmethanes with a 77.0 mol percent yield of 1,2,4-trimethylbenzene.

In runs similar to those shown in the examples, it was determined that other lower alkyl benzenes behave in substantially the same manner as the methyl benzenes in the process of the invention. Thus, the alkyl substituents on the alkyl benzene hydrocarbon charged to the condensation step may be either methyl, ethyl, propyl, or butyl groups. It is desirable that the alkyl carbon bonded to the benzene nucleus be either primary or secondary, since a tendency of tertiary alkyl groups to dealkylate during hydrogenolysis has been observed. This tendency is not so marked as to make the employment of tertiary alkyl benzene hydrocarbons inoperative, but it occurs to a sufficient extent to cause significant losses in yield.

In the condensation step the alkyl benzene is condensed with formaldehyde in the manner illustrated in the examples. Instead of the formaldehyde as illustrated, paraformaldehyde or trioxymethylene may be employed and, though less satisfactory than formaldehyde, methylal undergoesa similar condensation.

The condensation is preferably catalyzed by sulfuric acid which may be employed at concentrations ranging from about 40% to about 100% by weight. If dilute sulfuric acid is employed, water is desirably removed during the course of the condensation by distillation in the manner illustrated in Example 2. If more. concentrated sulfuric acid is employed, i. e., 90% by weight or higher, it is desirable to carry out the reaction in the presence of a diluent such as a lower aliphaticalcohol or acid, i. e., methanol, ethanol, glacial acetic acid, or the like. While sulfuric acid is preferred as the catalyst, other acid catalysts are effective, for example, phosphoric acid, trichloroacetic acid, ferricchloride, methane sulfonic acid, hydrofluoric acid, and the like.

The condensation can be accomplished at temperatures ranging from about 30 F. to 300 F. In general, lower temperatures are employed with the concentrated acid catalyst, i. e., sulfuric acid, at a concentration of 85% by weight or higher to avoid losses by sulfonation. If 50 to 70% sulfuric acid is employed, the condensation can be and desirably is carried out at temperatures ranging from 200 to 300 F.

Pursuant to the invention, the di-arylmethane condensation product produced in the first step of the process is cleaved by hydrogenolysis to produce alkyl benzenes. The term hydrogenolysis is recognized in the art as indicating the cleavage of a carbonto carbon bond accompanied by the addition of hydrogen. Hydrogenolysis is conventionally accomplished by contactinga feed and hydrogen with a hydrogenation catalyst under mild hydrogenating conditions. The hydrogenating conditions are sufficiently severe to cause cleavage of the carbon to carbon linkage in the di-arylmethane, but not sulficiently severe to cause ring hydrogenation.

The hydrogenolysis is desirably conducted at temperattires in the range from 650 to 900 F., preferably from 675 to -800 F.-, and at a pressure ranging from atmospheric to moderate superatmospheric pressures of the order of -250 p. s. i. g. At least-one molof hydrogen per mol of di-arylmethane is charged to the hydrogenolysis step. Preferably, however, a stoichiometric excess of hydrogen is employed ranging from about 3 mols of hydrogen to about 40 mols of hydrogen per mol of diarylmethane. The di-arylmethane and hydrogen are contacted with the hydrogenolysis catalyst at space velocities in the range from 0.1 to 10 liquid volumes of di-arylmethane per volume of catalyst per hour, preferably in the range from 0.5 to 3 v./v./hr.

In the conversion of di-arylmethanes to alkyl benzenes 'by'hydrogenolysis, the molybdenum oxide on alumina catalyst described in U. 8. Patents Nos. 2,432,286 and 2,481,824 are especially suitable. However, the metals of :groups VI-B, VII-B and VIII of the periodic table and their compounds, particularly the oxides and sulfides which are generally recognized as active hydrogenation catalysts, have also been found to effectively catalyze the hydrogenolysis of di-arylmethanes produced in Examples 1 to 8, inclusive, to alkyl benzenes. These active catalytic materials are commonly disposed on a carrier or support. In the process of theinvention it is desirable that the support be a. material which has relatively little catalytic cracking activity, for example, alumina or high rpurityfsilica-gel. The employment of high surface silica-alumina cracking catalysts as a support for the hydrogenation-catalysts is desirably avoided because this type of support acts as an isomeriz'ation catalyst and causes position isomerization of the ,polyalkyl benzene products so that the advantage of a high concentration of a particular position isomer in the product is lost in good part.

Weclaim:

1. A process for producing lower alkyl benzenes having'at least three lower alkyl groups attached to the henzene nucleus, which comprises condensing with formaldehyde a xylene isomer mixture feed in the presence of an acid catalyst to produce a diarylmethane hydrocarbon product, contacting the produced diarylmethane hydrocarbonproduct and hydrogen with a hydrogenation catalyst at from 650 F. to 900 F. and substan tially atmospheric pressure to eflfect hydrogenolysis of the diarylme'thane, and production of a reaction mixture comprising substituted benzene isomers having at least three lower alkyl groups substituted on the henzene nucleus, said reaction mixture being characterized by a very large predominance of one of said isomers, and recovering from said reaction mixture a fraction rich in said predominating isomer.

The method as defined in claim 1, wherein the aromatic hydrocarbon feed has a substantial content of pseudocumene.

3. A process for producing pseudocumene, which comprises condensing a mixture of xylene isomers with formaldehyde in the presence of an acid catalyst to produce a diarylmethane product, contacting the produced di-arylmethane product and hydrogen with a hydrogenation catalyst at a temperature in the range from about 650 F. to 900 F. and substantially atmospheric pressure to cause hydrogenolysis of the di-arylmethane producing-trimethyl benzenes characterized by a very large predominance of pseudocumene, and recovering pseudocumene from the hydrogenolysis reacti'onproduct.

4. A process as in claim 3, wherein pseudocumene produced is recycled to said condensing step and contacted with said mixture of xylene isomers and formaldehyde, and wherein durene is recovered from the hydrogenolysis reaction product.

5. A process forproducing durene, which comprises condensing pseudocumene with formaldehyde in the presence of an acid catalyst to produce a di arylmethane hydrocarbon product, contacting the produced di-arylmethane product and hydrogen with a hydrogenation catalyst at a temperature in the range from about 650 F. to 900 F. and substantially atmospheric pressure to cause hydrogenolysis of the di-arylmethane producing tetramethyl benzenes characterized by a very large predominance of durene, and recovering durene from the hydrogenolysis reaction product.

6. A process for producing durene, which comprises condensing a mixture of pseudocumene and a methyl benzene hydrocarbon selected from the group consisting of xylenes and toluene with formaldehyde in the presence of an acid catalyst to produce a di-arylmethane hydrocarbon product, contacting the produced di-arylmethane product and hydrogen with a hydrogenation catalyst at a temperature in the range from about 650 F. to 900 F. and substantially atmospheric pressure to cause hydrogenolysis of the di-arylmethane producing tetramethyl benzenes characterized by a very large predominance of durene, and recovering durene from the hydrogenolysis reaction product.

References Cited in the file of this patent UNITED STATES PATENTS 2,338,973 Schmerling 11111.11, 1944 2,394,751 Cole Feb. 12, 1945 FOREIGN PATENTS 446,450 Great Britain Apr. 30, 1946 OTHER REFERENCES 

1. A PROCESS FOR PRODUCING LOWER ALKYL BENZENES HAVING AT LEAST THREE LOWER ALKYL GROUPS ATTACHED TO THE BENZENE NUCLEUS, WHICH COMPRISES CONDENSING WITH FORMALDEHYDE A XYLENE ISOMER MIXTURE FEED IN THE PRESENCE OF AN ACID CATALYST TO PRODUCE A DIARYLMETHANE HYDROCARBON PRODUCT, CONTACTING THE PRODUCED DIARYLMETHANE HYDROCARBON PRODUCT AND HYDROGEN WITH A HYDROGENATION CATALYST AT FROM 650*F. TO 900*F. AND SUBSTANTIALLY ATMOSPHERIC PRESSURE TO EFFECT HYDROGENOLYSIS OF THE DIARYLMETHANE, AND PRODUCTION OF A REACTION MIXTURE COMPRISING SUBSTITUTED BENZENE ISOMERS HAVING AT LEAST THREE LOWER ALKYL GROUPS SUBSTITUTED ON THE BENZENE NUCLEUS, SAID REACTION MIXTURE BEING CHARACTERIZED BY A VERY LARGE PREDOMINANCE OF ONE OF SAID ISOMERS, AND RECOVERING FROM SAID REACTION MIXTURE A FRACTION RICH IN SAID PREDOMINATING ISOMER. 